1. Field of the Invention
The present invention relates to an interference removal method, and more particularly to inter-symbol interference (ISI) removal method in an orthogonal frequency division multiplexing (OFDM) system.
2. Description of the Related Art
Orthogonal frequency division multiplexing (OFDM) is a very effective technique to mitigate inter-symbol interference (ISI) in handling time dispersion of multipath fading channels. Conventionally, OFDM symbols are separated by cyclic prefix (CP) in order that receivers can demodulate data very simply. Recently, Time domain synchronous orthogonal frequency division multiplexing (TDS-OFDM) has been attracting more and more interests, in which pseudo-noise (PN) sequences take the place of CP for serving as guard intervals and also as training symbols. Chinese standard of digital terrestrial television broadcasting (DTTB), has adopted TDS-OFDM as one of its modulation schemes.
In TDS-OFDM systems, the inserted PN sequences acts as training symbols for the purposes of the receiver's synchronization and channel estimation, which makes it unnecessary to add pilots, as DVB-T system, in the transmitted signal spectrum. For this reason, basically TDS-OFDM can obtain higher channel throughout than CP-OFDM. Nevertheless, many algorithms in CP-OFDM including synchronization and channel estimation are so different that they cannot be applied to TDS-OFDM directly. In this paper, we will concentrate on the channel estimation and equalization in TDS-OFDM systems.